Modified Cellulose with BINAP-Supported Rh as an Efficient Heterogeneous Catalyst for Asymmetric Hydrogenation

Asymmetric catalysis is the preferred method for the synthesis of pure chiral molecules in the fine chemical industry. Cellulose has long been sought as a support in enantioselective catalysis. Dialdehyde cellulose (DAC) is produced by the selective oxidation of cellulose and is used to bind 5,5′-diamino Binap by forming a Schiff base. Here, we report the synthesis of modified cellulose-supported Rh as a novel biomass-supported catalyst and the characterization of its morphology, composition, and thermal stability. DAC-BINAP-Rh was a very effective catalyst in the asymmetric hydrogenation of enamides and could be easily recycled. This work provides a novel supported catalyst that broadens the applications of cellulose in asymmetric catalysis.

Carbene-catalyzed atroposelective synthesis of axially chiral styrenes

Axially chiral styrenes bearing a chiral axis between a sterically non-congested acyclic alkene and an aryl ring are difficult to prepare due to low rotational barrier of the axis. Disclosed here is an N-heterocyclic carbene (NHC) catalytic asymmetric solution to this problem. Our reaction involves ynals, sulfinic acids, and phenols as the substrates with an NHC as the catalyst. Key steps involve selective 1,4-addition of sulfinic anion to acetylenic acylazolium intermediate and sequential E-selective protonation to set up the chiral axis. Our reaction affords axially chiral styrenes bearing a chiral axis as the product with up to > 99:1 e.r., > 20:1 E/Z selectivity, and excellent yields. The sulfone and carboxylic ester moieties in our styrene products are common moieties in bioactive molecules and asymmetric catalysis.

Industrial Applications of Enzymes From Extremophiles

Extremophilic microorganisms have developed a variety of molecular tactics to exist in extreme environments. Researchers are fascinated by extremophiles and unearth various enzymes from these fascinating microbes. Extremozymes are astonishing biocatalysts with distinctive properties of catalysis and stability under a multitude of daunting conditions of salt, pH, organic solvents, and temperature, which open up new possibilities for biocatalysis and biotransformation and outcompetes mesophilic counterparts. Biotechnological implications include simple, immobilized, as well as whole-cell applications. Stability in organic solvents adds to the asymmetric catalysis and thereby exemplifies the applicability of extremozymes and in fostering biobased economies. Marine, cold-adapted enzymes, and those that help in the removal of a toxic hazardous substance from the environment are obvious choices for food industries and bioremediation. The major area of application and research emphasis includes textile, detergents, food, dairy, agriculture, and environmental remediation.

Enhanced N-directed electrophilic C-H borylation generates BN-[5]- and [6]helicenes with improved photophysical properties.

Helicenes are chiral polycyclic aromatic hydrocarbons (PAHs) of significant interest e.g. in supramolecular chemistry, materials science and asymmetric catalysis. Herein an enhanced N-directed electrophilic C-H borylation methodology has been developed...

Molecular Insights on Chirality Transfer from Double Axially Chiral Phosphoric Acid in a Synergistic Enantioselective Intramolecular Amination

In the most general practice of asymmetric catalysis, a chiral catalyst, typically bearing a center or an axis of chirality, is employed as the chiral source for imparting enantiocontrol over...

Nickel/brønsted acid dual-catalyzed regio- and enantioselective hydrophosphinylation of 1,3-dienes: access to chiral allylic phosphine oxides

While chiral allylic organophosphorus compounds are widely utilized in asymmetric catalysis and bioactive molecules, their synthetic methods are still very limited. We report the development of an asymmetric nickel/brønsted acid...

Asymmetric Synthesis of 2,3-Dihydrofurans via Squaramide Catalyzed Michael-Alkylation Reaction

Asymmetric Catalysis, Dihydrofuran, Michael-Alkylation Reaction, Tertiary Amine-Squaramide, Organocatalysis, α-Bromonitroalkene